title: Visual cortical gamma-band activity during free viewing of natural images.
abstract: Gamma-band activity in visual cortex has been implicated in several cognitive operations, like perceptual grouping and attentional selection. So far, it has been studied primarily under well-controlled visual fixation conditions and using well-controlled stimuli, like isolated bars or patches of grating. If gamma-band activity is to subserve its purported functions outside of the laboratory, it should be present during natural viewing conditions. We recorded neuronal activity with a 252-channel electrocorticographic (ECoG) grid covering large parts of the left hemisphere of 2 macaque monkeys, while they freely viewed natural images. We found that natural viewing led to pronounced gamma-band activity in the visual cortex. In area V1, gamma-band activity during natural viewing showed a clear spectral peak indicative of oscillatory activity between 50 and 80 Hz and was highly significant for each of 65 natural images. Across the ECoG grid, gamma-band activity during natural viewing was present over most of the recorded visual cortex and absent over most remaining cortex. After saccades, the gamma peak frequency slid down to 30-40 Hz at around 80 ms postsaccade, after which the sustained 50- to 80-Hz gamma-band activity resumed. We propose that gamma-band activity plays an important role during natural viewing.
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands Department of Neurological Surgery, University of Pittsburgh, PA 15213, USA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Brunet
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands Cognitive and Systems Neuroscience Group, Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
authors.forename: Conrado A
authors.initials: CA
authors.lastname: Bosman
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands Department of Neurocognition, University of Maastricht, 6229 ER Maastricht, The Netherlands and.
authors.forename: Mark
authors.initials: M
authors.lastname: Roberts
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands.
authors.forename: Robert
authors.initials: R
authors.lastname: Oostenveld
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands.
authors.forename: Thilo
authors.initials: T
authors.lastname: Womelsdorf
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands Department of Neurocognition, University of Maastricht, 6229 ER Maastricht, The Netherlands and.
authors.forename: Peter
authors.initials: P
authors.lastname: De Weerd
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society, 60528 Frankfurt, Germany.
authors.forename: Pascal
authors.initials: P
authors.lastname: Fries
mesh_terms: D000818:Animals; D000069280:Electrocorticography; D004567:Electrodes, Implanted; D065818:Gamma Rhythm; D008251:Macaca; D008297:Male; D010775:Photic Stimulation; D012438:Saccades / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: ECoG; free viewing; gamma; natural image; oscillation